Rules:
1. all non-zero digits are significant
2. all leading and following zeros are not significant
3. all zeros between two other digits are significant
4. any zero that follows a digit and is to the right of the decimal point is significant

When performing multiplication or division, the value with the fewest number of significant digits is the number of significant digits used in the final answer

When performing addition or subtraction, the value with the fewest number of digits after the decimal place represents the number of decimal places in the final answer

Scientific Notation: used for numbers greater than 1000 or less than 0.001

To use, move the decimal to be placed after the first non-zero digit
Count the number of decimal places moved
If the decimal has moved to the left, the exponent is positive
If the decimal has moved to the right, the exponent is negative

Trends of the Periodic Table

Trend 1 Atomic Radius:

– measured in picometers (1 X 10-12 m)
– distance from the nucleus to the valence orbital
– going right and up, the atomic radius decreases
– this is because going right, there is a greater force of attraction between the protons and electrons which makes a smaller radius
– going up the periodic table, there are less valence orbitals meaning the radius becomes smaller

Key Terms:

Shielding Effect: the effect of filled inner electron orbitals on the attractiveness of valence electrons to the nucleus

Effective Nuclear Charge: the apparent nuclear charge experienced by valence electrons, result of the shielding effect

Trend 2 Ionization Energy:

– amount of energy required to remove an electron
– going right and up on the periodic table will increase the ionization energy
– this is because fewer valence shells and more protons will make it require more energy to remove electrons

Trend 3 Electron Affinity:

– energy absorbed or released when an electron is added to a neutral atom
– going right and up the periodic table, the electron affinity will increase

Trend 4 Electronegativity:

– indicator of the relative ability of an atom to attract shared electrons
– smaller atomic radius usually means greater electronegativity
– going right and up the periodic table, electronegativity increases

Types of Bonds

Ionic:

– occurs between a metal and non-metal
– two ions bond to each other
– change in electronegativity is 1.7 – 3.3

Polar Covalent:

– occurs when non-metals share electrons
– has a positive and negative end
– change in electronegativity is 0.5 – 1.7

Covalent:

– occurs when non-metals share electrons
– does not have a positive/negative end
– change in electronegativity is 0 – 0.5

Properties of Ionic and Covalent Bonds

Ionic:

– high melting point
– does not conduct electricity as a solid
– conducts electricity in a solution
– high solubility in water
– solid state
– brittle, hard consistency as a solid

Covalent

– low melting point
– does not conduct electricity as a solid or in a solution
– not soluble in water
– non-polar compounds soluble in non-polar compounds
– polar compounds soluble in polar compounds
– can be solid, liquid, or gas
– soft, flexible, waxy consistency as a solid

Lewis Structures

– symbol of element is the center
– valence electrons are represented by dots surrounding the symbol of the element
– when dealing with ionic compounds, arrows are used to represent the loss/gain of electrons
– when dealing with covalent compounds, circles around electrons represent the sharing of electrons
– line structures simply use lines to show the sharing of electrons

Nomenclature/Balancing Equations

– will not be a major part of the test, so does not need to be reviewed too much